If you do not need Xdebug when running tests with PHPUnit, then you can disable it and run your tests much faster. However, it’s not easy for me to remember to disable Xdebug, so in my TestCase class I’ve overridden ´setUpBeforeClass´ and ´tearDownAfterClass´ like this:

    public static
    function setUpBeforeClass()
    {
        if ( function_exists('xdebug_disable') ) {
            xdebug_disable();
        }
    }

    public static
    function tearDownAfterClass()
    {
        if ( function_exists('xdebug_enable') ) {
            xdebug_enable();
        }
    }

That only toggles the backtrace, so the speed gain is less impressive, but for me is an acceptable trade-off.